This invention relates to a structure for a radio frequency shielding container, or container-like structure, and more particularly, to a latching mechanism by which a cover for such a container can be secured thereon and easily disengaged therefrom.
In the construction of various types of electrical or electronic circuitry it is often necessary to house certain components in containers or other such structures which are constructed and are of a material which will provide a shield against radio frequency energy. Such a shield might be necessary to prevent the radio frequency energy from impinging on the components in the container or to prevent radio frequency energy produced by the components in the container from reaching surrounding components. In the construction of such shielding containers, a removable cover must be provided to permit servicing or replacement of the components in the container. Since such containers are placed in a wide variety of environments and are subject to widely varying conditions, such as vibration or shock, it is necessary to provide a means by which the cover will be reliably secured under such conditions, but which will allow the cover to be easily removed.
The conventional forms of latching mechanisms presently being used include "dimples" either on the cover or on the container which engage with recesses on the other of the two members; this does not provide the reliable securing mechanism needed. Such dimples can be loosened, for example, by vibration. In other conventional forms of shielding containers, the container walls or the cover are equipped with tabs which can be bent over the other of these two members for securing purposes. The metals of which these tabs are usually made are such that repeated bending of the tabs generally causes weakening and breaking. Of course, it is possible to provide a securing mechanism in the form of screws and nuts extending through holes in the cover and container or through the use of other similar fastening devices. However, these fasteners constitute loose hardware when the container is opened which is subject to being lost and must be replaced. This can often prove difficult when servicing equipment having such containers, for example, in the field. In many instances, the cover is soldered, to the container, and this, of course, provides a generally reliable securing mechanism. However, this also constitutes a nearly permanent securing mechanism making the components in the container difficult to reach for servicing purposes.
Another common technique for providing a means for securing a cover to a container, such as the one here in question, is through the use of spring fingers placed either on the cover or in the container which are resiliently biased against the other of these two members. Thus, a resiliently urged friction grip is provided. While this is a convenient means for securing the cover, and one which permits ready removal, such a securing mechanism has been found to be generally unreliable when subject to unusual environmental conditions such as those mentioned above. An example of a securing mechanism of this type is to be found in U.S. Pat. No. 2,133,789 to E. J. Poole, issued Oct. 18, 1938.
It is, therefore, an object of this invention to provide a radio frequency shielding container structure having a latching mechanism for reliably securing a cover to the remainder of the container in such a way that the cover can easily be removed.
Another object of the invention is to provide in such a structure a latching mechanism which can be operated an indefinite number of time for removal of the cover without damaging the latching mechanism itself.
A further object of this invention is to provide in such a structure a latching mechanism which will reliably secure the cover to the container in such a way as to resist the effects of unusual environmental conditions, such as vibration or shock.
Another object of this invention is to provide in such a structure a latching mechanism which permits reliable securing of the cover to the container and ready removal without the use of loose hardware or the like which can easily be separated from the container when the cover is removed.
Still another object of this invention is to provide in such a structure a latching mechanism which can be produced at low cost, is simple to assemble without the use of special tools and meets the foregoing objects.